Improved mode of hardening and repairing files and rasps



UNITED STATES PATENT OFFICE.

GHARLES ADOLPHE'CITAVEL, OF PARIS, FRANCE.

lMPliOVED MODE 0F HARDENINQ ANDREPAIRING FILES AND RASPS.

Specification forming part of Letters Patent No. 43,658, dated July 26, 1864.

have invented a new and Improved Mode ofv Repairing Worn-Out Files and Rasps and ot' Hardening New Ones; and I dohereby declare that the followingis a full and exact description thereof.

The process above described has for its object repairing or recutting worn-out files and rasps and rendering them again fit for use, and hardening new files and rasps.

It consists, after having removed from their surface any foreign adherent matters, in int mersing the files and rasps in a bath formed of a mixture of sulphuric and nitric acids and water, the most efficacious proportions of which mixture are one part of nitric acid to three parts of sulphuric acid and seven parts of water, by measure. The only operation for new files and rasps is an immersion for a few seconds inthis mixture and the washings and neutralization of the effects of the acid,as will be hereinafter described. For the worn-out files andrasps the immersion lasts from about ten seconds to about five minutes, according to the more or less worn state of the file or rasp, theirsize,and,above all,theirfinenessorcoarsene'ss and hardness of metal, the sharpening or repairing being much more rapid for a fine soft-grained file than for a large-cut hardgrained file, which may require even a longer immersion than that above named. As the solution loses itsstrength by combining with the iron fresh doses'of acid must be added to it in the proportions above indicated. The rasps or files are next washed in clean water, passed through lime-water, dried in stoves or by other means, impregnated with a mixture of oil and turpentine by'means of a brush, and lastly brushed with coke-dust.

When it is necessary, to protect from the 20- tion of the acids certain parts of the file or rasp which are more worn away or lower than the rest amixture ,of sealing-wax and-fat-oil melted together is applied to these parts at a temperature of 30 centigrade, (63.6 Fahrenheit-,) or a varnish of gum-lac or other substance capable of'resisting the action of the acids. The immersion of the files or rasps in the acid bath should only takeplace thirty or forty hours after this application. When, on the contrary,'it is wished to cut away and level certain parts of the file'or rasp which project a mixture of a hundred parts of nitric acid with-fifty parts of sulphuric acid should be applied as many times as it may be necessary, while raising the tool at one end and inclining it toward the side, so that the acids may run into the grooves and deepen them without blunting the teeth. a Files and rasps may by the above means he sharpened several times and give each time a result at least equal, and in many instances superior, to new tiles and rasps.

hardening the surfaces of new files and-rasps,

substantially as above described.

CHARLES ADOLPHE OLAVEL.

Witnesses:

H. BONNEVILLE, 0. AUSTIER. 

